Thames21: Salmons Brook Project
Aquatic Invertebrate Survey Results
Date: 23/05/2013
Surveyors: Angela Bartlett and Giorgia Lombardi
Purpose: To record invertebrates (animals without a backbone) living in the Houndsden Stream at the Spinney and the stream into Boxers Lake and investigate water quality by looking at the number of invertebrates found and their species. Some species of invertebrates are much more tolerant of pollution than others.
Weather: Approximately 10°C with rain and hail at first sites.
Observations: Low flow, turbidity (cloudy water) and signs of pollution at all sites.
Method: We sieved and searched through 30cm2 of silt, gravel etc. (sediment) from the stream bed, using kick samples (agitating the stream bed and catching creatures in a net) where there was flowing water. We looked through the sediment at each site for 15mins and recorded the species found and numbers of invertebrates of each species.
Site / Species / Quantity / InterpretationBoxers Lake Stream C (downstream) / Biting midge larvae
Gammarus shrimp
Hog louse
Pond snail
Tubifex worm / 1
1
1
3
4 / No. of species found = 5
No. of invertebrates found = 10
Observations: Very fine sediment and extremely turbid (cloudy) water with an oily film. Lots of leaves and sticks etc. decaying in sediment.
Boxers Lake Stream B (middle) / Biting midge larvae
Chironomid (non-biting midge larvae)
Gammarus shrimp
Hog louse
Water spider
Tubifex worm / 1
2
2
5
1
2 / No. of species found = 6
No. of invertebrates found = 13
Observations: All life seemed to be in weed and algae rather than sediment.
Boxers Lake Stream A (upstream) / Hog louse (alive)
Hog louse (dead)
Non-biting midge larvae / 14
8
1 / No. of species found = 2
No. of invertebrates found = 23
Observations: Very polluted, lots of sewage fungus. Strong unnatural smell. Litter.
Houndsden Stream B (downstream) / Bivalve
Chironomid
Cranefly larvae
Hog louse (alive)
Hog louse (dead)
Non biting midge larvae
Pond snail
Tubifex worm / 1
10
1
9
3
5
1
12 / No. of species found = 7
No. of invertebrates found = 42
Observations: Relatively clear water, flowing faster due to smaller area, overhanging vegetation. Fine/ gravel sediment.
Houndsden Stream A (upstream) / Chironomid
Non biting midge larvae
Pond snail
Ramshorn snail
Tubifex worm
Worm / 4
3
1
1
6
5 / No. of species found = 6
No. of invertebrates found = 20
Observations: Relatively clear water, flowing faster over riffle features (stones on stream bed), overhanging vegetation. Fine/ gravel sediment. Sewage fungus growing on submerged plants.
Midge larvaeGammarus shrimpHoglouse
Pond snailTubifex worm Bivalve
Cranefly larvaeRamshorn snailWorm
Results: Only a few different species were found at each site. The species found are generally tolerant of low oxygen and relatively high pollution levels. The lack of species such as stoneflies, which are not tolerant of pollution and low oxygen levels, indicates that the water quality in these sites is generally poor, and is having a subsequent impact upon aquatic invertebrates. Boxers Lake Stream site A, had particularly bad results; low species richness but high numbers of one species does not indicate a healthy functioning ecosystem. At this site 23 invertebrates were found but 8 of these were dead, further evidence of poor water quality. We can conclude that water quality at all sites was poor, especially Boxers Lake Stream site A.